1. Field of the Invention
This invention relates generally to improvements in multiple glass sheet windows and, more particularly, to a double-sheet glass window having a space between the individual sheets, and including means for drying the air within the space and equalizing its pressure with the ambient atmosphere.
2. Description of the Prior Art
As is well known, multiple sheet window units have been widely used for reducing the transfer of heat and abating the transfer of sound. Such units generally comprise a pair of spaced glass sheets which are hermetically sealed together around their peripheral edges to form a dead-air space or chamber therebetween. This space or chamber may be filled with dehydrated air, other gas, or exhausted to provide a partial vacuum therein for preventing condensation of moisture upon the inside surfaces of the glass sheets. The efficiency of this style of window unit is dependent largely upon maintaining the space between the glass sheets hermetically sealed.
At least two major problems are presented by this style of window, one being the control of moisture condensation within the dead-air space and the other being pressure compensation of the air within the space. If the air or gas within the dead-air space contains even the slightest amount of water vapor, changes in the temperature and pressure of the air or gas within the space, and changes in the temperature of the glass sheets themselves may cause condensation to form on the inside surfaces of the glass sheets. Also, should the slightest leak develop permitting humid air to enter the space between the glass sheets and the ambient temperature drops, condensation of moisture occurs between the glass sheets. Since there is no circulation between the ambient air and the space between the glass sheets, the glass sheets will remain fogged for substantial periods of time which, of course, is quite detrimental to good visibility.
Concurrently, changes in the pressure of the air within the dead-air space, as well as changes in the ambient air pressure, exert varying forces on the glass sheets. When the sheets of glass employed in the units are relatively small, the effect of air pressure variations is of no concern. However, when the sheets of glass are relatively large, the glass sheets may be visibly distorted. In some instances, the flexing or bowing of the glass sheets is so pronounced as to spoil the aesthetic appearance of the units and, in other instances, the glass sheets may even be broken by the stresses generated by severe pressure variations.
Attempts have been made in the past to overcome these problems. For example, U.S. Pat. No. 3,001,249, issued to Elton et al. discloses a moisture-permeable plastic container containing a desiccant therein disposed within a hermetically sealed air space of the window unit. Elton et al. further discloses the use of a flexible plastic tube which functions to equalize the pressure within a closed space surrounding the hermetically sealed air space for mitigating rupturing or damage of the hermetic seal from extraneous forces.
U.S. Pat. No. 3,810,331, issued to McCurdy et al. discloses a dehydrating central air pressure system which communicates with the air spaces of a number of hermetically sealed dual-sheet windows for controlling the quantity of moisture of the air contained within the air spaces and the pressure thereof. Of course, this system is very costly, which prohibits its use when small numbers of dual window units are required, for example, in residential housing.
U.S. Pat. No. 3,570,201, issued to Barroero, discloses a curved two-pane door structure having a desiccant-containing breather tube for providing communication between the air space between the curved glass panes and the ambient atmosphere for controlling the moisture content and pressure of the air contained within the air space. However, this system is not entirely satisfactory as it is solely dependent upon the changes in ambient air pressures for its effectiveness.